I've made some major updates in my first post! Go check it out for my full reasonings on stage legality!
Here are some of the stages that I've edited in:
Shadow Moses Island: Neutral
I don't know about this one. The Metal Gear RAY might cause a potential problem, but we really didn't get too much information out of this stage's update. Either the Metal Gear RAY attacks opponents, or comes by and the players jump on it and ride. Or both?
When more stages are announced / shown in trailers, then I'll add to this list.
New Pork City: Banned
No question about it. Bigger than Hyrule Temple, and the Ultimate Chimera which delivers a one hit kill. It ain't happenin'. Though, I can see this stage being awesome for multiplayer. I liked Hyrule Temple to begin with; big stages are fuuuun.
Pictochat: Neutral
As far as we know, there's only one hazard involved with this stage. And by the looks of it, it doesn't look all too threatening. This stage is odd, but awesome at the same time. I'm just glad that there aren't any walk-to-K.O. parts in this stage (such as FlatZone).
Summit: Counterpick legal
This stage looks incredible, and I don't see much reason to not make it a banned stage (the fish is a little fishy, but we don't have too much info on it yet ;o). And as some of you might know, you can swim in Brawl. So the part of the level where the stage sinks probably won't cause to be too much of a problem.
Norfair: Banned
This stage isn't like Brinstar where the lava only rises from the bottom. Uh-uh, it comes from the sides, beneath, the top, and from behind. And during some of those events, there's almost no escape. Plus, if you even manage to make it into that safety-platform, that's DAMAGE CITY right there. I'd like to see an un-nerfed Peach rule the hill in there, mmhmm.
This thread needed a huge bump. It really is awesome.